A multi-quantum well-based light-emitting diode and a preparation method thereof

Abstract

The present invention discloses a multi-quantum well-based light-emitting diode and a preparation method thereof, including a substrate, and further including: a buffer layer, an undoped GaN layer, an N-type GaN layer, a multi-quantum well layer, an electron blocking layer, and a P-type GaN layer, which are sequentially stacked on the substrate; wherein, the multi-quantum well layer includes a plurality of periodically alternating stacks of quantum well layers and quantum barrier layers, the quantum well layer sequentially includes a first quantum well sub-layer, a second quantum well sub-layer, and a third quantum well sub-layer, and the first quantum well sub-layer is disposed on the N-type GaN layer; the first quantum well sub-layer includes a first GaN layer and a second GaN layer disposed on the first GaN layer, and the first GaN layer is disposed on the N-type GaN layer; the third quantum well sub-layer includes a first InGaN layer and a second InGaN layer disposed on the first InGaN layer, and the first InGaN layer is disposed on the second quantum well sub-layer. The present invention can solve the technical problem that the InGaN quantum well layer grown at low temperature in the prior art reduces the crystal quality of the multi-quantum well layer and affects the light-emitting efficiency of the multi-quantum well-based light-emitting diode.

Description

Technical Field

[0001] The present invention relates to the field of semiconductor optoelectronic technologies, and particularly to a multi-quantum well-based light-emitting diode and a preparation method thereof. Background Art

[0002] With the continuous development of semiconductor technologies, group III nitride semiconductors represented by gallium nitride (GaN) have received extensive attention as ideal materials for electronic and optoelectronic devices such as light-emitting diodes (LEDs), lasers (LDs), and high electron mobility transistors (HEMTs). Among them, multi-quantum well-based light-emitting diodes can change the bandgap width by adjusting the In composition of the multi-quantum well layer, so that their emission wavelengths can cover an extremely wide spectral range from near ultraviolet to near infrared.

[0003] Currently, the relatively common multi-quantum well-based light-emitting diodes use the multi-quantum well layer as the core light-emitting layer of the gallium nitride-based light-emitting diode. The electrons in the N-type semiconductor layer and the holes in the P-type semiconductor layer undergo radiative recombination in the multi-quantum well layer to achieve the emission of the gallium nitride-based light-emitting diode. The multi-quantum well layer includes a GaN quantum barrier layer and an InGaN quantum well layer. The performance of the multi-quantum well-based light-emitting diode is adjusted by adjusting the In composition of the InGaN quantum well layer. However, the In-N bond in the InGaN quantum well layer is very weak. When the temperature is heated to 800 °C, the thermal activation energy generated reaches the dissociation activation energy of the In-N bond. The incorporation of In is very sensitive to the growth temperature of the quantum well layer. Therefore, in order to obtain an InGaN quantum well layer with a high In composition, a relatively low epitaxial growth temperature is often used. However, NH3, as the N source of the InGaN quantum well layer, has a significant reduction in the cracking rate of NH3 at a relatively low temperature, and the active N source is severely insufficient. At the same time, low temperature will also reduce the atomic mobility, resulting in uneven growth of InGaN. The combined effect of the two leads to a significant reduction in the crystal quality of the InGaN quantum well layer grown at low temperature. These crystal defects provide channels for non-radiative recombination, reduce the radiative recombination efficiency of electrons and holes, and reduce the emission efficiency of the multi-quantum well-based light-emitting diode.

[0004] Therefore, the existing multi-quantum well-based light-emitting diodes generally have the technical problem that the InGaN quantum well layer grown at low temperature reduces the crystal quality of the multi-quantum well layer and affects the emission efficiency of the multi-quantum well-based light-emitting diode. Summary of the Invention

[0005] Aiming at the deficiencies of the prior art, the purpose of the present invention is to provide a multi-quantum well-based light-emitting diode and a preparation method thereof, aiming to solve the technical problem that the InGaN quantum well layer grown at low temperature in the prior art reduces the crystal quality of the multi-quantum well layer and affects the emission efficiency of the multi-quantum well-based light-emitting diode.

[0006] One aspect of the present invention is to provide a multi-quantum-well-based light-emitting diode, which comprises:

[0007] A buffer layer, an undoped GaN layer, an N-type GaN layer, a multi-quantum-well layer, an electron blocking layer, and a P-type GaN layer, which are sequentially stacked on the substrate;

[0008] Wherein, the multi-quantum-well layer comprises a plurality of periodically alternating stacks of quantum well layers and quantum barrier layers, the quantum well layer sequentially comprises a first quantum well sub-layer, a second quantum well sub-layer, and a third quantum well sub-layer, and the first quantum well sub-layer is disposed on the N-type GaN layer;

[0009] The first quantum well sub-layer comprises a first GaN layer and a second GaN layer disposed on the first GaN layer, and the first GaN layer is disposed on the N-type GaN layer;

[0010] The third quantum well sub-layer comprises a first InGaN layer and a second InGaN layer disposed on the first InGaN layer, and the first InGaN layer is disposed on the second quantum well sub-layer.

[0011] Compared with the prior art, the beneficial effects of the present invention are as follows: through a multi-quantum well-based light-emitting diode provided by the present invention, the quantum well layer is arranged in multiple layers, improving the crystal quality of the quantum well layer and avoiding the situation where only the InGaN layer grown at low temperature is used as the quantum well layer, which leads to a reduction in the crystal quality of the quantum well layer, a decrease in the radiative recombination efficiency of electrons and holes, and thus a reduction in the luminous efficiency of the light-emitting diode. Specifically, the quantum well layer sequentially includes a first quantum well sub-layer, a second quantum well sub-layer, and a third quantum well sub-layer. The first quantum well sub-layer includes a first GaN layer and a second GaN layer disposed on the first GaN layer. The third quantum well sub-layer includes a first InGaN layer and a second InGaN layer disposed on the first InGaN layer. The first InGaN layer is disposed on the second quantum well sub-layer. The first quantum well sub-layer improves the crystal quality before the second quantum well sub-layer through the first GaN layer and the second GaN layer, facilitating the growth of subsequent epitaxial layers. The second quantum well sub-layer reduces the lattice mismatch between the N-type GaN layer and the third quantum well sub-layer, further improving the crystal quality of the third quantum well sub-layer. The third quantum well sub-layer improves the incorporation of In atoms through the first InGaN layer and improves the uniformity of In atoms through the second InGaN layer, preventing In atom clustering and improving the atomic mobility, thereby improving the crystal quality of the third quantum well sub-layer. Under the combined action of the first quantum well sub-layer, the second quantum well sub-layer, and the third quantum well sub-layer, the crystal quality of the quantum well layer is significantly improved, and the radiative recombination of electrons and holes increases, thereby improving the efficiency of the light-emitting diode. Thus, the technical problem that the InGaN quantum well layer grown at low temperature generally reduces the crystal quality of the multi-quantum well layer and affects the luminous efficiency of the multi-quantum well-based light-emitting diode is solved.

[0012] According to one aspect of the above technical solution, the thickness of the quantum well layer is 2 - 5 nm.

[0013] According to one aspect of the above technical solution, the thickness ratio of the first GaN layer, the second GaN layer, the second quantum well sub-layer, the first InGaN layer, and the second InGaN layer is 1 - 2:1:1:4 - 8:1 - 2.

[0014] According to one aspect of the above technical solution, the second quantum well sub-layer is an InGaN thin film layer with a gradually changing In composition, the In composition is 0.01 - 0.5, and the In composition gradually increases from the side close to the first quantum well sub-layer to the side far from the first quantum well sub-layer.

[0015] According to one aspect of the above technical solution, the first GaN layer is a GaN thin film layer grown at a constant temperature, and the growth temperature is 820 - 880 °C. The second GaN layer is a GaN thin film layer grown with a gradually decreasing temperature, and the growth temperature drops by 20 - 50 °C.

[0016] According to one aspect of the above technical solution, the first InGaN layer is an InGaN thin film layer grown at a constant temperature, and the growth temperature is 750 - 830 °C. The second InGaN layer is an InGaN thin film layer grown with a gradually increasing temperature, and the growth temperature increases by 50 - 100 °C.

[0017] According to one aspect of the above technical solution, the In component of the first InGaN layer is 0.05 - 0.5, and the In component of the second InGaN layer is 0.05 - 0.5.

[0018] Another aspect of the present invention lies in providing a method for manufacturing a multi - quantum - well - based light - emitting diode. The manufacturing method is used to manufacture the multi - quantum - well - based light - emitting diode according to any one of claims 1 - 8. The manufacturing method includes:

[0019] Providing a substrate;

[0020] Growing a buffer layer, an undoped GaN layer, and an N - type GaN layer on the substrate in sequence;

[0021] Epitaxially growing a multi - quantum - well layer on the N - type GaN layer. Among them, the multi - quantum - well layer sequentially includes a plurality of periodically alternating stacks of quantum - well layers and quantum - barrier layers. The quantum - well layer sequentially includes a first quantum - well sub - layer, a second quantum - well sub - layer, and a third quantum - well sub - layer. The first quantum - well sub - layer is grown on the N - type GaN layer. The first quantum - well sub - layer includes a first GaN layer and a second GaN layer grown on the first GaN layer. The first GaN layer is grown on the N - type GaN layer. The third quantum - well sub - layer includes a first InGaN layer and a second InGaN layer grown on the first InGaN layer. The first InGaN layer is grown on the second quantum - well sub - layer;

[0022] Growing an electron - blocking layer and a P - type GaN layer on the multi - quantum - well layer in sequence.

[0023] Further explanation, the growth step of the quantum - well layer includes:

[0024] Gradually reducing the temperature at a rate of 40 - 60 °C / min, and the growth temperature drops by 20 - 50 °C. During the temperature reduction process, epitaxially grow the second GaN layer on the first GaN layer;

[0025] Continue to reduce the temperature at a rate of 40 - 60 °C / min, and the growth temperature drops by 20 - 50 °C. During the temperature reduction process, epitaxially grow the second quantum - well sub - layer on the second GaN layer;

[0026] Set the temperature to 750 - 830 °C, set the pressure to 100 - 500 Torr, and grow the first InGaN layer on the second quantum well sublayer, where the component of In is 0.05 - 0.5;

[0027] Gradually increase the temperature at a heating rate of 90 - 110 °C / min, increase the growth temperature by 50 - 100 °C, and epitaxially grow the second InGaN layer on the first InGaN layer during the heating process, where the component of In is 0.05 - 0.5. Brief Description of the Drawings

[0028] The above and / or additional aspects and advantages of the present invention will become obvious and easy to understand from the description of the embodiments in conjunction with the following drawings, where:

[0029] Figure 1 is a schematic structural diagram of a multi - quantum - well - based light - emitting diode in the first embodiment of the present invention;

[0030] Figure 2 is a schematic structural diagram of a quantum well layer in the first embodiment of the present invention;

[0031] Figure 3 is a flowchart of a method for manufacturing a multi - quantum - well - based light - emitting diode in the eighth embodiment of the present invention;

[0032] Description of the Symbols of the Components in the Drawings:

[0033] Substrate 100, buffer layer 200, undoped GaN layer 300, N - type GaN layer 400, multi - quantum - well layer 500, quantum well layer 510, first quantum well sublayer 511, second quantum well sublayer 512, third quantum well sublayer 513, first GaN layer 514, second GaN layer 515, first InGaN layer 516, second InGaN layer 517, quantum barrier layer 520, electron blocking layer 600, P - type GaN layer 700. Detailed Description of the Embodiments

[0034] To make the objectives, features, and advantages of the present invention more obvious and understandable, the following detailed description of the specific embodiments of the present invention is provided in conjunction with the drawings. Several embodiments of the present invention are given in the drawings. However, the present invention can be implemented in many different forms and is not limited to the embodiments described herein. On the contrary, the purpose of providing these embodiments is to make the disclosure of the present invention more thorough and comprehensive.

[0035] It should be noted that when an element is referred to as being "fixed to" another element, it can be directly on the other element or there can also be an intermediate element. When an element is considered to be "connected" to another element, it can be directly connected to the other element or there may be an intermediate element at the same time. The terms "vertical", "horizontal", "left", "right", "up", "down" and similar expressions used herein are only for the purpose of illustration, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and thus should not be construed as a limitation on the present invention.

[0036] In the present invention, unless otherwise clearly defined and limited, terms such as "installed", "connected", "joined", "fixed", etc. should be understood in a broad sense. For example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be directly connected or indirectly connected through an intermediate medium, and it can be the communication inside two elements. For those of ordinary skill in the art, the specific meanings of the above terms in the present invention can be understood according to specific circumstances. The term "and / or" used herein includes any and all combinations of one or more of the related listed items.

[0037] Embodiment 1

[0038] Please refer to Figure 1 - Figure 2 , which shows a multi-quantum-well-based light-emitting diode provided by the first embodiment of the present invention. The multi-quantum-well-based light-emitting diode includes a substrate 100; wherein, the substrate 100 is a substrate for epitaxial layer growth. Commonly used substrates 100 are sapphire substrates, SiO2 sapphire composite substrates, silicon substrates, silicon carbide substrates, gallium nitride substrates, and zinc oxide substrates. In this embodiment, the material of the substrate 100 is sapphire. Sapphire has the advantages of good light transmission performance, high temperature resistance, corrosion resistance, mature preparation process, and low price, and is widely used in multi-quantum-well-based light-emitting diodes.

[0039] A buffer layer 200, an undoped GaN layer 300, an N-type GaN layer 400, a multi-quantum well layer 500, an electron blocking layer 600, and a P-type GaN layer 700 are sequentially stacked on a substrate 100. Among them, the buffer layer 200 is an AlN thin film layer with a thickness of 10 - 50 nm. The buffer layer 200 is used to relieve the lattice mismatch and thermal mismatch between the substrate 100 and the subsequent grown epitaxial layer, reduce crystal defects, and improve the crystal quality of the subsequent epitaxial layer. Usually, the substrate 100 on which the buffer layer 200 is deposited needs to be pretreated to remove surface impurities and improve the crystal quality of the buffer layer 200. Specifically, the substrate 100 on which the buffer layer 200 has been deposited is placed in a reaction chamber, the temperature is set to 1000 - 1200 °C, and it is treated in an H2 environment for 1 - 10 min to remove surface impurities, and then the substrate 100 is nitrided to improve the crystal quality of the buffer layer 200, thereby effectively improving the crystal quality of the subsequently grown epitaxial layer.

[0040] Among them, an undoped GaN layer 300 is provided on the buffer layer 200 with a thickness of 2 - 3 μm. As the thickness of the GaN increases, the compressive stress will be released through stacking faults, the line defects will decrease, and the crystal quality will improve. For commercially produced LED epitaxial wafers, a thickness of about 2 - 3 μm is usually a relatively optimized thickness, which not only saves production costs but also improves the crystal quality of the undoped GaN layer 300. Specifically, the temperature is set to 1050 - 1200 °C, the pressure is set to 100 - 600 Torr, and an undoped GaN layer with a thickness of 2 - 3 μm is grown on the buffer layer 200.

[0041] In addition, an N-type GaN layer 400 is provided on the undoped GaN layer 300. The N-type GaN layer 400 provides electrons to the multi-quantum well layer 500 so that electrons and holes radiatively recombine in the multi-quantum well layer 500 to achieve the light-emitting effect of the multi-quantum well-based light-emitting diode. Its thickness is 2 - 3 μm. The dopant of the N-type GaN layer 400 is Si, and the doping concentration is 1×10 19 -5×10 19 cm -3 . Through the doping of the dopant, the N-type GaN layer 400 can reduce the current crowding effect and improve the optoelectronic efficiency of the multi-quantum well-based light-emitting diode. Specifically, the temperature is set to 1050 - 1200 °C, the pressure is set to 100 - 600 Torr, the dopant is Si, and the doping concentration is 1×10 19 -5×10 19 cm -3 , and an N-type GaN layer 400 with a thickness of 2 - 3 μm is grown on the undoped GaN layer.

[0042] Among them, a multi-quantum well layer 500 is provided on the N-type GaN layer 400. Electrons provided by the N-type GaN layer 400 and holes provided by the P-type GaN layer 700 undergo radiative recombination in the multi-quantum well layer 500 to achieve the emission of the multi-quantum well-based light-emitting diode. The multi-quantum well layer 500 includes a plurality of periodically alternating stacked quantum well layers 510 and quantum barrier layers 520. The period of the multi-quantum well layer 500 is 5-15. The multi-period multi-quantum well layer 500 can increase the overlap of electron-hole wave functions, improve the radiative recombination efficiency, and enhance the luminous efficiency of the multi-quantum well-based light-emitting diode. Among them, the quantum well layer 510 sequentially includes a first quantum well sub-layer 511, a second quantum well sub-layer 512, and a third quantum well sub-layer 513. The first quantum well sub-layer 511 is disposed on the N-type GaN layer 400. The first quantum well sub-layer 511 includes a first GaN layer 514 and a second GaN layer 515 disposed on the first GaN layer 514. The first GaN layer 514 is disposed on the N-type GaN layer 400. The third quantum well sub-layer 513 includes a first InGaN layer 516 and a second InGaN layer 517 disposed on the first InGaN layer 516. The first InGaN layer 516 is disposed on the second quantum well sub-layer 512. The thickness of this quantum well is 2-5 nm. The thickness ratio of the first GaN layer 514, the second GaN layer 515, the second quantum well sub-layer 512, the first InGaN layer 516, and the second InGaN layer 517 is 1-2:1:1:4-8:1-2.

[0043] It should be noted that when the thickness of the quantum well layer 510 exceeds 5 nm, a polarization electric field will be generated, resulting in the spatial separation of electrons and holes, a reduction in the overlap integral of the electron-hole wave functions, and a significant decrease in the radiative recombination efficiency. When the thickness of the quantum well is less than 2 nm, the concentrations of electrons and holes in the quantum well layer 510 will be reduced, and the radiative recombination efficiency of electrons and holes will be decreased.

[0044] Among them, the first GaN layer 514 is a GaN thin film layer grown at a constant temperature, and the second GaN layer 515 is a GaN thin film layer grown with a gradually decreasing temperature. The growth temperature of the first GaN layer 514 is relatively high, and the growth temperature is 820-880 °C. The second GaN layer 515 is formed by growing while cooling after the growth of the first GaN layer 514 is completed, and the growth temperature drops by 20-50 °C to reduce the defects inside the thin film layer, thereby improving the crystal quality of the first quantum well sub-layer 511 and further improving the crystal quality of the epitaxial layer grown subsequently. Specifically, the temperature is heated to 820-880 °C, the pressure is set to 100-500 Torr, and the first GaN layer 514 is epitaxially grown on the N-type GaN layer 400; the temperature is gradually decreased, the cooling rate is 40-60 °C / min, and the growth temperature drops by 20-50 °C. During the cooling process, the second GaN layer 515 is epitaxially grown on the first GaN layer 514.

[0045] In addition, a second quantum well sub-layer 512 is provided on the first quantum well sub-layer 511. The second quantum well sub-layer 512 is an InGaN thin film layer with a gradually changing In composition. The In composition is 0.01 - 0.5, and the In composition gradually increases from the side close to the first quantum well sub-layer to the side far from the first quantum well sub-layer, gradually increasing the concentration of In atoms. From the first quantum well sub-layer 511 to the second quantum well sub-layer 512, it gradually transitions from GaN material to InGaN material to reduce the lattice mismatch between the GaN material and the InGaN material, so as to alleviate the lattice mismatch between the N-type GaN layer 400 and the third quantum well sub-layer 513 and improve the crystal quality of the third quantum well sub-layer 513. The second quantum well sub-layer 512 is grown while cooling down after the growth of the second GaN layer 515, and the growth temperature drops by 20 - 50 °C to reduce the defects inside the thin film layer, thereby improving the crystal quality of the second quantum well sub-layer 512 and further improving the crystal quality of the epitaxial layer grown subsequently. Specifically, after the growth of the second GaN layer 515, continue to cool down at a cooling rate of 40 - 60 °C / min, and the growth temperature drops by 20 - 50 °C. During the cooling process, the second quantum well sub-layer 512 is epitaxially grown on the second GaN layer 515.

[0046] The settings of the first quantum well sub-layer 511 and the second quantum well sub-layer 512 ensure that the crystal quality before the growth of the third quantum well sub-layer 513 reaches the optimum, so as to improve the crystal quality of the third quantum well sub-layer 513. At the same time, it also alleviates the lattice mismatch between the N-type GaN layer 400 and the third quantum well sub-layer 513, thereby improving the crystal quality of the third quantum well sub-layer 513, improving the crystal quality of the quantum well layer 510, and reducing the non-radiative recombination of electrons and holes.

[0047] Among them, a third quantum well sub-layer 513 is provided on the second quantum well sub-layer 512. The third quantum well sub-layer 513 includes a first InGaN layer 516 and a second InGaN layer 517 provided on the first InGaN layer 516. The first InGaN layer 516 is grown on the second quantum well sub-layer 512. The growth temperature of the first InGaN layer 516 is relatively low, being 750 - 830 °C, and the In component is 0.05 - 0.5. Growing the first InGaN layer 516 at a relatively low temperature is conducive to the incorporation of In, improving the radiative recombination of holes and electrons, thereby improving the efficiency of the multi-quantum well-based light-emitting diode. The second InGaN layer 517 is formed by growing while raising the temperature after the growth of the first InGaN layer 516 is completed. The growth temperature is increased by 50 - 100 °C, and the heating rate is 90 - 110 °C / min, and the In component is 0.05 - 0.5. Growing the second InGaN layer 517 while raising the temperature can reduce the internal defects of the third quantum well sub-layer 513, improve the crystal quality of the third quantum well sub-layer 513. At the same time, it can reduce the In component segregation caused by the low-temperature growth of the first InGaN layer 516, reduce In clusters, improve the atomic mobility, enhance the crystal quality and uniformity of the third quantum well sub-layer 513, thereby improving the radiative recombination efficiency of holes and electrons in the quantum well layer 510, avoiding using only the low-temperature-grown InGaN layer as the quantum well layer 510, increasing the crystal defects of the quantum well layer 510, increasing the non-radiative recombination efficiency of electrons and holes, and reducing the light-emitting efficiency of the multi-quantum well-based light-emitting diode.

[0048] Specifically, the temperature is set to 750 - 830 °C, the pressure is set to 100 - 500 Torr, and the first InGaN layer 516 is grown on the second quantum well sub-layer 512, where the In component is 0.05 - 0.5; the temperature is gradually increased, the heating rate is 90 - 110 °C / min, and the growth temperature is increased by 50 - 100 °C. During the heating process, the second InGaN layer 517 is epitaxially grown on the first InGaN layer 516, where the In component is 0.05 - 0.5.

[0049] It can be understood that the multi-layer setting of the quantum well layer 510 will improve the crystal quality of the quantum well layer 510, thereby improving the electron-hole recombination efficiency and the light-emitting efficiency of the multi-quantum well-based light-emitting diode. The first quantum well sub-layer 511 improves the crystal quality before the second quantum well sub-layer 512 through the first GaN layer 514 and the second GaN layer 515, which is beneficial to the growth of subsequent epitaxial layers. The second quantum well sub-layer 512 is an InGaN thin film layer with a gradually changing In composition. From the first quantum well sub-layer 511 to the second quantum well sub-layer 512, it gradually transitions from a GaN material to an InGaN material, reducing the lattice mismatch between the GaN thin film layer and the InGaN thin film layer, and reducing the lattice mismatch between the N-type GaN layer 400 and the third quantum well sub-layer 513, further improving the crystal quality of the third quantum well sub-layer 513. The third quantum well sub-layer 513 improves the incorporation of In atoms through the first InGaN layer 516 and improves the uniformity of In atoms through the second InGaN layer 517, preventing In atom clustering and improving atomic mobility, thereby improving the crystal quality of the third quantum well sub-layer 513. Under the combined action of the first quantum well sub-layer 511, the second quantum well sub-layer 512, and the third quantum well sub-layer 513, the crystal quality of the quantum well layer 510 is significantly improved, and the radiative recombination of electrons and holes increases, thereby improving the efficiency of the light-emitting diode and avoiding the poor crystal quality of the quantum well layer 510 caused by only growing the InGaN layer at a low temperature as the quantum well layer 510, reducing the electron-hole radiative recombination efficiency, and reducing the light-emitting efficiency of the multi-quantum well-based light-emitting diode.

[0050] In the preferred embodiment of this example, the thickness of the quantum well layer 510 is 3.5 nm, and the thickness ratio of the first GaN layer 514, the second GaN layer 515, the second quantum well sub-layer 512, the first InGaN layer 516, and the second InGaN layer 517 is 1.5:1:1:4:1. The In composition of the second quantum well sub-layer 512 gradually changes from 0.05 to 0.25 from low to high. The In composition of the first InGaN layer 516 is 0.25, and the In composition of the second InGaN layer 517 is 0.25. The growth temperature of the first GaN layer 514 is 850 °C, the growth temperature of the second GaN layer 515 decreases from 850 °C to 810 °C while growing, the growth temperature of the second quantum well sub-layer 512 decreases from 810 °C to 795 °C while growing, the growth temperature of the first InGaN layer 516 is 795 °C, and the growth temperature of the second InGaN layer 517 increases from 795 °C to 870 °C.

[0051] In addition, a quantum barrier layer 520 is provided on the quantum well layer 510. By alternately stacking the quantum well layer 510 and the quantum barrier layer 520 in multiple periods to form multiple quantum wells, radiative recombination of holes and electrons is achieved. The quantum barrier layer 520 is an AlGaN thin film layer with a thickness of 8.5 - 10.5 nm and an Al component of 0.01 - 0.1. Specifically, the temperature is set to 800 - 900 °C, the pressure is set to 100 - 300 Torr, and a quantum barrier layer 520 with a thickness of 8.5 - 10.5 nm is grown on the quantum well layer 510, where the Al component is 0.01 - 0.1.

[0052] An electron blocking layer 600 is provided on the multiple quantum well layer 500 to limit electron overflow. Since the rate of electron migration is faster than that of hole migration, the electron blocking layer 600 can effectively prevent the electrons in the N-type GaN layer 400 from overflowing to the P-type GaN layer 700, preventing non-radiative recombination of electrons and holes in the P-type GaN layer 700 and reducing the luminous efficiency of the multiple quantum well-based light-emitting diode. The electron blocking layer 600 is an Al x In y Ga 1-x-y N thin film layer with a thickness of 10 - 40 nm, where the Al component x is 0.005 - 0.5 and the In component y is 0.05 - 0.2. Specifically, the temperature is set to 900 - 1000 °C, the pressure is set to 100 - 300 Torr, and an electron blocking layer 600 with a thickness of 10 - 40 nm is grown on the multiple quantum well layer 500, where the Al component x is 0.005 - 0.5 and the In component y is 0.05 - 0.2.

[0053] In addition, a P-type GaN layer 700 is provided on the electron blocking layer 600. The P-type GaN layer 700 provides holes to the multiple quantum well layer 500 to enable radiative recombination of electrons and holes in the multiple quantum well layer 500, achieving the light-emitting effect of the multiple quantum well-based light-emitting diode. The thickness of the P-type GaN layer 700 is 10 - 50 nm, the dopant is Mg, and the doping concentration is 1×10 19 -1×10 21 cm -3 . Specifically, the temperature is set to 900 - 1050 °C, the pressure is set to 100 - 600 Torr, the dopant is Mg, and the doping concentration is 1×10 19 -1×10 21 cm -3 , and a P-type GaN layer 700 with a thickness of 10 - 50 nm is grown on the electron blocking layer 600.

[0054] Compared with the prior art, a multi-quantum-well-based light-emitting diode provided in this embodiment has the beneficial effects that: through the multi-quantum-well-based light-emitting diode provided by the present invention, the quantum well layer is arranged in multiple layers, improving the crystal quality of the quantum well layer and avoiding the situation where only the InGaN layer grown at low temperature is used as the quantum well layer, which leads to a reduction in the crystal quality of the quantum well layer, a decrease in the radiative recombination efficiency of electrons and holes, and thus a reduction in the light-emitting efficiency of the multi-quantum-well-based light-emitting diode. Specifically, the quantum well layer sequentially includes a first quantum well sub-layer, a second quantum well sub-layer, and a third quantum well sub-layer. The first quantum well sub-layer includes a first GaN layer and a second GaN layer disposed on the first GaN layer. The third quantum well sub-layer includes a first InGaN layer and a second InGaN layer disposed on the first InGaN layer. The first InGaN layer is disposed on the second quantum well sub-layer. The first quantum well sub-layer improves the crystal quality before the second quantum well sub-layer through the first GaN layer and the second GaN layer, facilitating the growth of subsequent epitaxial layers. The second quantum well sub-layer reduces the lattice mismatch between the N-type GaN layer and the third quantum well sub-layer, further improving the crystal quality of the third quantum well sub-layer. The third quantum well sub-layer improves the incorporation of In atoms through the first InGaN layer and improves the uniformity of In atoms through the second InGaN layer, preventing In atom clustering and improving the atomic mobility, thereby improving the crystal quality of the third quantum well sub-layer. Under the combined action of the first quantum well sub-layer, the second quantum well sub-layer, and the third quantum well sub-layer, the crystal quality of the quantum well is significantly improved, and the radiative recombination of electrons and holes increases, thereby improving the efficiency of the multi-quantum-well-based light-emitting diode. Thus, the technical problem that the crystal quality of the multi-quantum-well layer is reduced by the InGaN quantum well layer grown at low temperature, which affects the light-emitting efficiency of the multi-quantum-well-based light-emitting diode, is solved.

[0055] Embodiment 2

[0056] A multi-quantum-well-based light-emitting diode provided in the second embodiment of the present invention is different from the multi-quantum-well-based light-emitting diode in the first embodiment in that:

[0057] The thickness of the quantum well layer is 3.2 nm. Under the same other conditions, the thickness ratio of the first GaN layer, the second GaN layer, the second quantum well sub-layer, the first InGaN layer, and the second InGaN layer is 1.5:1:1:4:1. The In composition of the second quantum well sub-layer gradually changes from 0.05 to 0.25 from low to high. The In composition of the first InGaN layer is 0.25, the In composition of the second InGaN layer is 0.25. The growth temperature of the first GaN layer is 850 °C, the growth temperature of the second GaN layer decreases from 850 °C to 810 °C while growing, the growth temperature of the second quantum well sub-layer decreases from 810 °C to 795 °C while growing, the growth temperature of the first InGaN layer is 795 °C, and the growth temperature of the second InGaN layer increases from 795 °C to 870 °C.

[0058] Example 3

[0059] A multi-quantum well-based light-emitting diode provided by the third embodiment of the present invention. The difference between the multi-quantum well-based light-emitting diode in this embodiment and the multi-quantum well-based light-emitting diode in the first embodiment is as follows:

[0060] The thickness of the quantum well layer is 3.7 nm. Under the same other conditions, the thickness ratio of the first GaN layer, the second GaN layer, the second quantum well sub-layer, the first InGaN layer, and the second InGaN layer is 1.5:1:1:4:1. The In composition of the second quantum well sub-layer gradually changes from 0.05 to 0.25 from low to high. The In composition of the first InGaN layer is 0.25, the In composition of the second InGaN layer is 0.25. The growth temperature of the first GaN layer is 850 °C, the growth temperature of the second GaN layer decreases from 850 °C to 810 °C while growing, the growth temperature of the second quantum well sub-layer decreases from 810 °C to 795 °C while growing, the growth temperature of the first InGaN layer is 795 °C, and the growth temperature of the second InGaN layer increases from 795 °C to 870 °C.

[0061] Example 4

[0062] A multi-quantum well-based light-emitting diode provided by the fourth embodiment of the present invention. The difference between the multi-quantum well-based light-emitting diode in this embodiment and the multi-quantum well-based light-emitting diode in the first embodiment is as follows:

[0063] The thickness ratio of the first GaN layer, the second GaN layer, the second quantum well sub-layer, the first InGaN layer, and the second InGaN layer is 1:1:1:4:1. Under the same other conditions, the thickness of this quantum well layer is 3.5 nm. The In composition of the second quantum well sub-layer gradually changes from 0.05 to 0.25 from low to high. The In composition of the first InGaN layer is 0.25, the In composition of the second InGaN layer is 0.25, the growth temperature of the first GaN layer is 850 °C, the growth temperature of the second GaN layer decreases from 850 °C to 810 °C while growing, the growth temperature of the second quantum well sub-layer decreases from 810 °C to 795 °C while growing, the growth temperature of the first InGaN layer is 795 °C, and the growth temperature of the second InGaN layer increases from 795 °C to 870 °C.

[0064] Example Five

[0065] A multi-quantum well-based light-emitting diode provided by the fifth embodiment of the present invention. The difference between the multi-quantum well-based light-emitting diode in this embodiment and the multi-quantum well-based light-emitting diode in the first embodiment is that:

[0066] The thickness ratio of the first GaN layer, the second GaN layer, the second quantum well sub-layer, the first InGaN layer, and the second InGaN layer is 2:1:1:4:1. Under the same other conditions, the thickness of this quantum well layer is 3.5 nm. The In composition of the second quantum well sub-layer gradually changes from 0.05 to 0.25 from low to high. The In composition of the first InGaN layer is 0.25, the In composition of the second InGaN layer is 0.25, the growth temperature of the first GaN layer is 850 °C, the growth temperature of the second GaN layer decreases from 850 °C to 810 °C while growing, the growth temperature of the second quantum well sub-layer decreases from 810 °C to 795 °C while growing, the growth temperature of the first InGaN layer is 795 °C, and the growth temperature of the second InGaN layer increases from 795 °C to 870 °C.

[0067] Example Six

[0068] A multi-quantum well-based light-emitting diode provided by the sixth embodiment of the present invention. The difference between the multi-quantum well-based light-emitting diode in this embodiment and the multi-quantum well-based light-emitting diode in the first embodiment is that:

[0069] The growth temperature of the first GaN layer is 845 °C. The growth temperature of the second GaN layer decreases from 845 °C to 815 °C while growing. The growth temperature of the second quantum well sub-layer decreases from 815 °C to 795 °C while growing. Under the same other conditions, the thickness ratio of the first GaN layer, the second GaN layer, the second quantum well sub-layer, the first InGaN layer and the second InGaN layer is 1.5:1:1:4:1. The thickness of this quantum well layer is 3.5 nm. The In composition of the second quantum well sub-layer gradually changes from 0.05 to 0.25 from low to high. The In composition of the first InGaN layer is 0.25, and the In composition of the second InGaN layer is 0.25. The growth temperature of the first InGaN layer is 795 °C, and the growth temperature of the second InGaN layer increases from 795 °C to 870 °C.

[0070] Example VII

[0071] A multi-quantum well-based light-emitting diode provided by the seventh embodiment of the present invention is different from the multi-quantum well-based light-emitting diode in the first embodiment in that:

[0072] The growth temperature of the first GaN layer is 855 °C. The growth temperature of the second GaN layer decreases from 855 °C to 810 °C while growing. The growth temperature of the second quantum well sub-layer decreases from 810 °C to 795 °C while growing. Under the same other conditions, the thickness ratio of the first GaN layer, the second GaN layer, the second quantum well sub-layer, the first InGaN layer and the second InGaN layer is 1.5:1:1:4:1. The thickness of this quantum well layer is 3.5 nm. The In composition of the second quantum well sub-layer gradually changes from 0.05 to 0.25 from low to high. The In composition of the first InGaN layer is 0.25, and the In composition of the second InGaN layer is 0.25. The growth temperature of the first InGaN layer is 795 °C, and the growth temperature of the second InGaN layer increases from 795 °C to 870 °C.

[0073] Comparative Example I

[0074] A multi-quantum well-based light-emitting diode provided by the first comparative example of the present invention is different from the multi-quantum well-based light-emitting diode in the first embodiment in that:

[0075] The quantum well layer is only a conventional InGaN thin film layer grown at low temperature.

[0076] Please refer to Table 1 below, which shows the corresponding parameters of the above-mentioned Embodiments 1 to 7 and Comparative Example I of the present invention.

[0077] Table 1

[0078]

[0079]

[0080] It should be noted that the chips prepared in Examples 1 to 7 and Comparative Example 1 were all prepared into 10 mil × 24 mil chips under the same process conditions. 300 chips were respectively extracted and their performance was tested under a current of 120 mA / 60 mA.

[0081] Combining the data of Examples 1 to 7 and Comparative Example 1, it can be seen that using a multi-layer structure for the quantum well layer will improve the luminescence efficiency of the quantum well layer, that is, improve the radiative recombination efficiency of electrons and holes, improve the crystal quality of the quantum well layer, and avoid the poor crystal quality of the quantum well layer in Comparative Example 1 where the quantum well layer is only a low-temperature InGaN layer, resulting in low luminescence efficiency of the multi-quantum well-based light-emitting diode.

[0082] Combining the data of Examples 1, 2, and 3, it can be seen that when the thickness of the quantum well layer is too thick, when it increases from 3.5 nm to 3.8 nm, the increase in luminescence efficiency decreases from 1.5% to 1.2%, which will lead to the spatial separation of electrons and holes, reduce the overlap integral of the wave functions of electrons and holes, and reduce the radiative efficiency, thus affecting the luminescence efficiency of the multi-quantum well-based light-emitting diode. When the thickness of the quantum well layer is too thin, when it decreases from 3.5 nm to 3.2 nm, the increase in luminescence efficiency decreases from 1.5% to 0.8%, which will reduce the concentration of electrons and holes in the quantum well layer and reduce the radiative recombination efficiency of electrons and holes, thus affecting the luminescence efficiency of the multi-quantum well-based light-emitting diode.

[0083] Combining the data of Examples 1, 4, and 5, it can be seen that when the thickness of the first GaN layer is too high, when the thickness ratio increases from 1.5:1:1:4:1 to 2:1:1:4:1, the increase in luminescence efficiency decreases from 1.5% to 1.1%. Since the total thickness of the quantum well remains unchanged, it will directly affect the thickness of the second quantum well sub-layer and the third quantum well sub-layer. The reduction of the second quantum well sub-layer will lead to an inability to sufficiently reduce the lattice mismatch between the N-type GaN layer and the third quantum well sub-layer. At the same time, the third quantum well sub-layer is too thin to introduce enough In atoms. Both will result in poor crystal quality of the quantum well layer, thus reducing the luminescence efficiency of the multi-quantum well-based light-emitting diode. When the thickness of the first GaN layer is too thin, when the thickness ratio increases from 1.5:1:1:4:1 to 1:1:1:4:1, the increase in luminescence efficiency decreases from 1.5% to 1%. The thinning of the first GaN layer will not be able to ensure the optimal crystal growth of the second quantum well sub-layer and the third quantum well sub-layer, and cannot fill the crystal defects and dislocations brought by the N-type GaN layer, affecting the crystal quality of the first quantum well sub-layer, thus resulting in poor crystal quality of the quantum well layer and affecting the luminescence efficiency of the multi-quantum well-based light-emitting diode.

[0084] Combining the data of Example 1, Example 6 and Example 7, it can be seen that the growth temperature of the first quantum well sublayer will affect the light-emitting efficiency of the multi-quantum well-based light-emitting diode, that is, it directly affects the crystal quality of the quantum well layer. When the growth temperature of the first GaN layer increases from 850 °C to 855 °C, the cooling rate of the subsequent growth of the second GaN layer is too fast, resulting in poor crystal quality of the second GaN layer, reducing the crystal quality of the first quantum well sublayer, and affecting the light-emitting efficiency of the multi-quantum well-based light-emitting diode; when the growth temperature of the first GaN layer decreases from 850 °C to 845 °C, the growth of the first GaN layer is not dense enough, resulting in a reduction in the crystal quality of the first quantum well sublayer, affecting the crystal quality of the quantum well layer, and thus leading to a decrease in the light-emitting efficiency of the multi-quantum well-based light-emitting diode.

[0085] In summary, using a multi-layered quantum well layer will improve the crystal quality of the quantum well layer, increase the radiative recombination of electrons and holes, thereby improving the efficiency of the light-emitting diode, and avoiding the poor crystal quality of the quantum well layer caused by only growing the InGaN layer at a low temperature, reducing the radiative recombination efficiency of electrons and holes, and reducing the light-emitting efficiency of the multi-quantum well-based light-emitting diode.

[0086] Example 8

[0087] Please refer to Figure 3 , which shows a method for manufacturing a multi-quantum well-based light-emitting diode according to the eighth embodiment of the present invention. The manufacturing method includes steps S10 - S13:

[0088] Step S10, providing a substrate;

[0089] Among them, the substrate is a sapphire substrate. The sapphire substrate has the advantages of good light transmittance, high temperature resistance, corrosion resistance, mature manufacturing process and low price, and is widely used in multi-quantum well-based light-emitting diodes.

[0090] Step S11, sequentially growing a buffer layer, an undoped GaN layer and an N-type GaN layer on the substrate;

[0091] Among them, when growing a buffer layer on the substrate, the buffer layer is an AlN thin film layer with a thickness of 10 - 50 nm. The buffer layer is used to relieve the lattice mismatch and thermal mismatch between the substrate and the subsequent grown epitaxial layer, reduce crystal defects, and improve the crystal quality of the subsequent epitaxial layer.

[0092] When growing an undoped GaN layer on the buffer layer, specifically, the temperature is set to 1050 - 1200 °C, the pressure is set to 100 - 600 Torr, and an undoped GaN layer with a thickness of 2 - 3 μm is grown on the buffer layer.

[0093] An N-type GaN layer is grown on an undoped GaN layer. The N-type GaN layer provides electrons to the multiple quantum well layer, enabling electrons and holes to radiatively recombine in the multiple quantum well layer, achieving the light-emitting effect of the multiple quantum well-based light-emitting diode.

[0094] Specifically, the temperature is set to 1050 - 1200 °C, the pressure is set to 100 - 600 Torr, the dopant is Si, and the doping concentration is 1×10 19 -5×10 19 cm -3 , and an N-type GaN layer with a thickness of 2 - 3 μm is grown on the undoped GaN layer.

[0095] Step S12, epitaxially grow a multiple quantum well layer on the N-type GaN layer. Among them, the multiple quantum well layer sequentially includes a plurality of periodically alternating stacks of quantum well layers and quantum barrier layers. The quantum well layer sequentially includes a first quantum well sub-layer, a second quantum well sub-layer, and a third quantum well sub-layer. The first quantum well sub-layer grows on the N-type GaN layer. The first quantum well sub-layer includes a first GaN layer and a second GaN layer grown on the first GaN layer. The first GaN layer grows on the N-type GaN layer. The third quantum well sub-layer includes a first InGaN layer and a second InGaN layer grown on the first InGaN layer. The first InGaN layer grows on the second quantum well sub-layer;

[0096] Among them, the thickness of the quantum well layer is 2 - 5 nm, and the thickness ratio of the first GaN layer, the second GaN layer, the second quantum well sub-layer, the first InGaN layer, and the second InGaN layer is 1 - 2:1:1:4 - 8:1 - 2.

[0097] Grow the first quantum well sub-layer on the N-type GaN layer. The first quantum well sub-layer includes a first GaN layer and a second GaN layer grown on the first GaN layer. The first quantum well sub-layer reduces the defects inside the thin film layer, thereby improving the crystal quality of the first quantum well sub-layer, and thus improving the crystal quality of the subsequent grown epitaxial layer.

[0098] Specifically, heat the temperature to 820 - 880 °C, set the pressure to 100 - 500 Torr, and epitaxially grow the first GaN layer on the N-type GaN layer; gradually lower the temperature, with a cooling rate of 40 - 60 °C / min, and the growth temperature drops by 20 - 50 °C. During the cooling process, epitaxially grow the second GaN layer on the first GaN layer.

[0099] The second quantum well sub-layer is grown on the first quantum well sub-layer. The second quantum well sub-layer is an InGaN thin film layer with a gradually changing In composition. The In composition ranges from 0.01 to 0.5, and the In composition gradually increases from the side close to the first quantum well sub-layer to the side far from the first quantum well sub-layer, gradually increasing the concentration of In atoms. From the first quantum well sub-layer to the second quantum well sub-layer, it gradually transitions from GaN material to InGaN material to reduce the lattice mismatch between GaN material and InGaN material, alleviate the lattice mismatch between the N-type GaN layer and the third quantum well sub-layer, improve the crystal quality of the third quantum well sub-layer. Under the combined action of the first quantum well sub-layer and the second quantum well sub-layer, the crystal quality of the thin film layer before growing the third quantum well sub-layer reaches the optimum, which is beneficial to the growth of the third quantum well sub-layer.

[0100] Specifically, after growing the second GaN layer, the temperature continues to decrease, and the cooling rate is 40 - 60 °C / min, and the growth temperature drops by 20 - 50 °C. During the cooling process, the second quantum well sub-layer is epitaxially grown on the second GaN layer.

[0101] The third quantum well sub-layer is grown on the second quantum well sub-layer. The third quantum well sub-layer includes a first InGaN layer and a second InGaN layer grown on top of the first InGaN layer. The first InGaN layer is conducive to the incorporation of In, improving the radiative recombination of holes and electrons. The second InGaN layer can reduce the internal defects of the third quantum well sub-layer, improve the crystal quality of the third quantum well sub-layer. At the same time, it can reduce the In composition segregation caused by the low-temperature growth of the first InGaN layer, reduce In clusters, improve the atomic mobility, enhance the crystal quality and uniformity of the third quantum well sub-layer, thereby improving the radiative recombination efficiency of holes and electrons in the quantum well layer, avoiding using only the low-temperature grown InGaN layer as the quantum well layer, increasing the crystal defects in the quantum well layer, increasing the non-radiative recombination efficiency of electrons and holes, and reducing the luminous efficiency of the multi-quantum well-based light-emitting diode.

[0102] Specifically, the temperature is set to 750 - 830 °C, and the pressure is set to 100 - 500 Torr. The first InGaN layer is grown on the second quantum well sub-layer, where the In composition is 0.05 - 0.5; the temperature is gradually increased, and the heating rate is 90 - 110 °C / min, and the growth temperature increases by 50 - 100 °C. During the heating process, the second InGaN layer is epitaxially grown on the first InGaN layer, where the In composition is 0.05 - 0.5.

[0103] In addition, a quantum barrier layer is grown on the third quantum well sub-layer, and a multi-quantum well is formed by alternately stacking multiple periods of the quantum well layer and the quantum barrier layer to achieve radiative recombination of holes and electrons. The quantum barrier layer is an AlGaN thin film layer with a thickness of 8.5 - 10.5 nm and an Al component of 0.01 - 0.1. Specifically, the temperature is set to 800 - 900 °C, the pressure is set to 100 - 300 Torr, and a quantum barrier layer with a thickness of 8.5 - 10.5 nm is grown on the quantum well layer, where the Al component is 0.01 - 0.1.

[0104] Step S13, an electron blocking layer and a P-type GaN layer are sequentially grown on the multi-quantum well layer.

[0105] An electron blocking layer is grown on the multi-quantum well layer to limit electron overflow.

[0106] Specifically, the temperature is set to 900 - 1000 °C, the pressure is set to 100 - 300 Torr, and an Al x In y Ga 1-x-y N thin film layer with a thickness of 10 - 40 nm is grown on the multi-quantum well layer as the electron blocking layer, where the Al component x is 0.005 - 0.5 and the In component y is 0.05 - 0.2.

[0107] A P-type GaN layer is grown on the electron blocking layer. The P-type GaN layer provides holes to the multi-quantum well layer, enabling electrons and holes to radiatively recombine in the multi-quantum well layer to achieve the light-emitting effect of the multi-quantum well-based light-emitting diode. Specifically, the temperature is set to 900 - 1050 °C, the pressure is set to 100 - 600 Torr, the dopant is Mg, and the doping concentration is 1×10 19 -1×10 21 cm -3 , and a P-type GaN layer with a thickness of 10 - 50 nm is grown on the electron blocking layer.

[0108] Compared with the prior art, the preparation method of a multi-quantum-well-based light-emitting diode provided in this embodiment has the beneficial effects that: through the preparation method of the multi-quantum-well-based light-emitting diode provided by the present invention, the quantum wells are grown in multiple layers. Through the combined action of growing the first quantum well sub-layer and the second quantum well sub-layer, the crystal quality of the thin film layer before growing the third quantum well sub-layer reaches the optimum, and at the same time, the lattice mismatch between the N-type GaN layer and the third quantum well sub-layer is reduced to improve the crystal quality of the third quantum well sub-layer. The third quantum well sub-layer improves the incorporation of In atoms by growing the first InGaN layer, and improves the uniformity of In atoms and prevents In atom clustering and improves the atomic mobility by growing the second InGaN layer, thereby improving the crystal quality of the third quantum well sub-layer, thus improving the crystal quality of the multi-quantum-well layer, increasing the radiative recombination efficiency of electron-hole pairs, improving the light-emitting efficiency of the multi-quantum-well-based light-emitting diode, and avoiding that only growing the InGaN thin film layer at low temperature as the quantum well layer results in a reduction in the crystal quality of the quantum well layer and a reduction in the radiative recombination efficiency of electrons and holes. Thereby, the technical problem that the crystal quality of the multi-quantum-well layer is reduced by the InGaN quantum well layer grown at low temperature, which affects the light-emitting efficiency of the multi-quantum-well-based light-emitting diode, is solved.

[0109] In the description of this specification, the descriptions referring to terms such as "one embodiment", "some embodiments", "examples", "specific examples", or "some examples" etc. mean that the specific features, structures, materials, or characteristics described in connection with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representations of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials, or characteristics described can be combined in a suitable manner in any one or more embodiments or examples.

[0110] The above-described embodiments merely represent several implementation manners of the present invention, and their descriptions are relatively specific and detailed, but should not be construed as limiting the scope of the patent of the present invention. It should be noted that for those of ordinary skill in the art, without departing from the concept of the present invention, several modifications and improvements can still be made, and these all belong to the protection scope of the present invention. Therefore, the protection scope of the patent of the present invention should be subject to the appended claims.

Claims

1. A multi-quantum well-based light-emitting diode, comprising a substrate, characterized in that, The multi-quantum well-based light-emitting diode further includes: A buffer layer, an undoped GaN layer, an N-type GaN layer, a multi-quantum well layer, an electron blocking layer, and a P-type GaN layer that are sequentially stacked on the substrate; Wherein, the multi-quantum well layer includes a plurality of periodically alternating stacks of quantum well layers and quantum barrier layers. The quantum well layer sequentially includes a first quantum well sub-layer, a second quantum well sub-layer, and a third quantum well sub-layer. The first quantum well sub-layer is disposed on the N-type GaN layer; The first quantum well sub-layer includes a first GaN layer and a second GaN layer disposed on the first GaN layer. The first GaN layer is disposed on the N-type GaN layer; The third quantum well sub-layer includes a first InGaN layer and a second InGaN layer disposed on the first InGaN layer. The first InGaN layer is disposed on the second quantum well sub-layer. The second quantum well sub-layer is an InGaN thin film layer with a gradually changing In molar ratio. The In molar ratio is 0.01-0.5, and the In molar ratio gradually increases from the side close to the first quantum well sub-layer to the side far from the first quantum well sub-layer.

2. The multi-quantum well-based light emitting diode according to claim 1, wherein The thickness of the quantum well layer is 2-5 nm.

3. The multi-quantum well-based light emitting diode according to claim 1, wherein The thickness ratio of the first GaN layer, the second GaN layer, the second quantum well sub-layer, the first InGaN layer, and the second InGaN layer is 1-2:1:1:4-8:1-2.

4. The multi-quantum well-based light-emitting diode according to claim 1, wherein The first GaN layer is a GaN thin film layer grown at a constant temperature, and the growth temperature is 820-880 °C. The second GaN layer is a GaN thin film layer grown with a gradually decreasing temperature, and the growth temperature decreases by 20-50 °C.

5. The multi-quantum well-based light-emitting diode according to claim 1, wherein, The first InGaN layer is an InGaN thin film layer grown at a constant temperature, and the growth temperature is 750-830 °C. The second InGaN layer is an InGaN thin film layer grown with a gradually increasing temperature, and the growth temperature increases by 50-100 °C.

6. The multi-quantum well-based light-emitting diode according to claim 5, characterized in that, The In molar ratio of the first InGaN layer is 0.05-0.5, and the In molar ratio of the second InGaN layer is 0.05-0.

5.

7. The multi-quantum well-based light-emitting diode according to claim 1, characterized in that, The quantum barrier is an AlGaN thin film layer with a thickness of 8-12 nm, and the Al molar ratio is 0.01-0.

1.

8. A method for preparing a multi-quantum well-based light-emitting diode, characterized in that, The preparation method is used to prepare the multi-quantum well-based light-emitting diode according to any one of claims 1-7. The preparation method includes: Providing a substrate; Growing a buffer layer, an undoped GaN layer, and an N-type GaN layer on the substrate in sequence; A multi - quantum well layer is epitaxially grown on the N - type GaN layer. Among them, the multi - quantum well layer sequentially includes a plurality of periodically alternating stacked quantum well layers and quantum barrier layers. The quantum well layer sequentially includes a first quantum well sub - layer, a second quantum well sub - layer, and a third quantum well sub - layer. The first quantum well sub - layer is grown on the N - type GaN layer. The first quantum well sub - layer includes a first GaN layer and a second GaN layer grown on the first GaN layer. The first GaN layer is grown on the N - type GaN layer. The third quantum well sub - layer includes a first InGaN layer and a second InGaN layer grown on the first InGaN layer. The first InGaN layer is grown on the second quantum well sub - layer. The second quantum well sub - layer is an InGaN thin film layer with a gradually changing In molar ratio. The In molar ratio is 0.01 - 0.5, and the In molar ratio gradually increases from the side close to the first quantum well sub - layer to the side far from the first quantum well sub - layer; An electron blocking layer and a P - type GaN layer are sequentially grown on the multi - quantum well layer.

9. The method for preparing a multi-quantum well-based light-emitting diode according to claim 8, wherein, The growth step of the quantum well layer includes: Heat the temperature to 820 - 880 °C, set the pressure to 100 - 500 Torr, and epitaxially grow the first GaN layer on the N - type GaN layer; Gradually lower the temperature at a rate of 40 - 60 °C / min, and the growth temperature drops by 20 - 50 °C. During the temperature - lowering process, epitaxially grow the second GaN layer on the first GaN layer; Continue to lower the temperature at a rate of 40 - 60 °C / min, and the growth temperature drops by 20 - 50 °C. During the temperature - lowering process, epitaxially grow the second quantum well sub - layer on the second GaN layer; Set the temperature to 750 - 830 °C, set the pressure to 100 - 500 Torr, and grow the first InGaN layer on the second quantum well sub - layer, where the molar ratio of In is 0.05 - 0.5; Gradually raise the temperature at a rate of 90 - 110 °C / min, and the growth temperature rises by 50 - 100 °C. During the temperature - raising process, epitaxially grow the second InGaN layer on the first InGaN layer, where the molar ratio of In is 0.05 - 0.5.

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